I’m a novice in this field; I hope someone experienced in automatic control can explain the boiler control system. Please help! !
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①The boiler is not equipped with a PLC; it is controlled by a DCS system. The burner sequential control and safety interlock protection are in the SIS system. ②The burner is controlled by a separate programmer (burning control system), while the boiler’s operational processes are managed by the boiler’s PLC system. Modbus communication is used between the PLC and the DCS, and the Modbus TCP/IP protocol is employed for tasks involving logic. ③The boiler is controlled by a separate PLC, and the burners are also controlled by PLCs; the control logic for the burners requires safety integrity certification (SIL). The PLCs communicate with the DCS for display purposes. From the perspective of process operation, how will these three types of automatic control affect on-site and central control operations? In particular, after changing the first option to the second, does this mean that adjustable panels will remain in the on-site PLC cabinet for the fuel gas system and boiler load?
The first option is to perform all operations entirely within the DCS, with interlocks handled by the SIS； The second approach is to retain on-site control, with the display on the DCS achieved through communication; the logic is controlled via communication on the DCS ； The third option is that the information is displayed only on the DCS via communication; the DCS does not perform any control, and control is carried out entirely at the site. After changing the first type to the second, a control panel can be available on-site for control.
I understand a bit now. It seems that the level of automation is decreasing step by step. Given the current level of design and automation, achieving full DCS control (i.e., the first option) should not be difficult.
There are no difficulties per se, but there are issues in other aspects. One of them is the operating habits of the technical staff; many prefer to carry out control tasks on-site. Additionally, boiler manufacturers provide control PLCs as part of their products. If they were to remove those PLCs, their profits would decrease. The factory’s procurement staff does not have knowledge in this area, so unless there is a request from the instrumentation department, the equipment delivered will still come with PLCs. With the construction of smart factories today, all systems need to be integrated, and information must be collected via OPC and sent to the MES. I believe that removing the PLCs and integrating them into the DCS, as well as integrating interlocks into the SIS, is a good approach.
Yes. Perhaps our considerations are limited to the site alone. They were also considering other issues.
At present, the operations that can be carried out on-site are mainly those in special situations; normal adjustments are performed via the DCS, while in emergency situations, relevant SIS or BMS systems ensure proper functioning.
The first is that CNC is not allowed in the SIS system； For the second and third methods, pay attention to the timeliness of communication between PLCs and DCSes; the communication efficiency of Modbus is particularly low
I’m a student majoring in automatic control, and I still haven’t figured out how to control boilers.